From: Axel Polleres <axel.polleres@deri.org>

Date: Wed, 03 Jun 2009 13:22:23 +0100

Message-ID: <4A266AFF.7020004@deri.org>

To: Jos de Bruijn <debruijn@inf.unibz.it>

CC: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

Date: Wed, 03 Jun 2009 13:22:23 +0100

Message-ID: <4A266AFF.7020004@deri.org>

To: Jos de Bruijn <debruijn@inf.unibz.it>

CC: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

* I am fine to keep the DL-safeness definitition "as is" for LC. * I guess the point on the semicolon in the definition of multistructures requires Michael Kifer's response. Axel Jos de Bruijn wrote: > > Axel Polleres wrote: >> find my comments inline below. This completes ACION-830 >> http://www.w3.org/2005/rules/wg/track/actions/830 >> >> Overall, I am fine with most of the changes made wrt. >> Urgent open points: >> >> - DL-safeness definition. >> >> - Semantic multistructures and dl-multi-structures still look >> inconsistent. >> >> more comments below. >> > > > My responses in-line. > >>>> Section 3.1 >>>> =========== >>>> >>>> * Section 3.1.2 "A RIF-RDF combination consists of a RIF document and >>>> zero or more RDFgraphs" >>>> >>>> Why do we allow only 1 RIF dcoument and arbitrary RDF graphs in a >>>> combination? >>> Because an RIF document an import any number of RDF graphs. >> >> >> I am not sure whether I understand this reply, but what I >> asked was why not several RIF documents can be involved, but ... > > Section 5 says how to interpret an RIF document importing a number of > RDF graphs. There is only one RIF document involved here, and so there > is no point to define the semantics for combinations involving more than > one RIF document. > >>>> This means that simple entailment in combination with an empty >>>> ruleset is not the same as simple entailment in RDF... I think that >>>> should be pointed out explicitly. It would be also worthwhile to add >>>> this example, >>>> i.e. I suggest to add (at the end of Section 3.2.3): >>>> "Note that simple entailment in combination with an empty ruleset is >>>> not the same as simple entailment in RDF, since certain entailments >>>> regarding datatypes are enforced by the RIF-BLD semantics in >>>> combinations. For instance, given two graphs >>>> >>>> G1= { :s :p "foo" .} and >>>> G2= { :s :p "foo"^^xs:string } >>>> >>>> as well as an empty RIF document R. >>>> >>>> G1 |=/=_simpleRDF G2 >>>> following [http://link-to-rdf-mt-simple-entailment RDF simple >>>> entailment] , but >>>> >>>> <R,{G1}> |=_simple <R,{G2}> >>>> " >>> There is already an example to this effect in the introduction to >>> section 3. >> >> Then at least a pointer would be worthwhile here, so a short version >> >> "Note that simple entailment in combination with an empty ruleset >> is not the same as simple entailment in RDF, since certain entailments >> regarding datatypes are enforced by the RIF-BLD semantics in >> combinations, cf. also Example [pointer-to-example] before." > > done > >>>> Section 4: >>>> ========== >>>> >>>> >>>> * Section 4.1.1 >>>> "Given a set of OWL 2 DL ontologies O, a variable ?x in a RIF rule Q H >>>> :- B is DL-safe if it occurs in an atomic formula in B that is not of >>>> the form s[P -> o] or s[rdf:type -> A], where P or A occurs in one of >>>> the ontologies in O." >>>> >>>> That doesn't seem to be sufficient, take: >>>> >>>> ?X [rdf:type -> d ] :- Or ( ?X [rdf:type -> c ] p(?X) ) >>>> >>>> this is DL-safe according to the definition above but can be expanded >>>> to two rule one of which wouldn't be DL-safe. >>>> >>>> Rather, we need to adopt a safeness notion similar to Core. >>> You are right. The definition is not sufficient. For now I just defined >>> it for disjunction-free rules. I hope I will be able to include a proper >>> safeness condition later on. You can also have a go at it, if you feel >>> like it. >> Didn't manage to tackle it either, and will likely not be able this >> week, sorry. > > Do you think it is critical to have the refined definition in place > before LC? I think it is OK to refine the definition later, since it is > already at risk. > >>>> * Section 4.2.2.1 >>>> >>>> >>>> * >>>> Definition (dl-semantic multi-structure): >>>> "I<sub>1C</sub>, ..., I<sub>1C</sub>" >>>> >>>> looks weird, better use 1...n as superscripts as in >>>> http://www.w3.org/2005/rules/wiki/BLD#def-bld-semantic-multistruct >>>> >>>> Again, shouldn't we use \hat{I} rather than I for >>>> multi-structures as in BLD to be consistent? >>>> >>>> * >>>> same definition: >>>> Bullet 1 ends with "and ; " >>>> That looks incomplete, is there anything missing? >>>> >>>> * >>>> "I(φ), for any other formula or symbol φ, and the truth >>>> valuation >>>> function TValI are defined as in BLD semantic structures. " >>>> >>>> I am, honestly, getting confused with the definitions of >>>> multi-structures in BLD vs. SWC. >>>> >>>> dl-multistructures consist of {I_1, ..., I_n} >>>> whereas BLD multistructures are {J,I; I_i1, I_i2, ...} >>>> so, I am unsure what "defined as in BLD semantic structures." >>>> means to say. >>>> >>>> (BTW: I sent an amendment to my BLD review per mail in this regard >>>> as well) >>> I updated the definition in SWC to reflect the changes in the definition >>> in BLD. Please have a look. >> >> - semantic multistructures and dl-multi0-structures still look >> inconsistent: >> >> section 4.2.2.1 >> >> >> " >> Formally, a dl-semantic multi-structure Î is a set of dl-semantic >> structures {J,I, Ii1, Ii2, ...}, where " >> >> misses th ";" used in BLD... shouldn't this be: >> >> "Formally, a dl-semantic multi-structure Î is a set of dl-semantic >> structures {J,I; Ii1, Ii2, ...}, where " >> >> ? > > To be honest, I don't understand the ';'. It is a set, and the ',' is > commonly used to separate the individual elements in a set. > >> >> - same here: >> >> "Given a dl-semantic multi-structure Î={I1, I2, ...}, " >> >> should be: >> >> "Given a dl-semantic multi-structure Î={{J,I; Ii1, Ii2, ...}, " > > It is a set of structures, so it does not really matter which symbols I > use for the individual elements. > > > Cheers, Jos > -- Dr. Axel Polleres Digital Enterprise Research Institute, National University of Ireland, Galway email: axel.polleres@deri.org url: http://www.polleres.net/Received on Wednesday, 3 June 2009 12:23:01 UTC

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